The TCP/IP Protocol Stack
A stack of protocols, layered on top of each other, that together allow forming connections between clients and servers over a large network composed of many small and heterogenous networks.
Each protocol uses a lower-level protocol to send its own packets. The packet of each protocol looks generally like this:
The "data" or "payload" part will contain a packet formed by a higher-level protocol. This method is called "protocol encapsulation".